Chuck unit for automatic machine tools, designed to perform both power tasks and finishing work

ABSTRACT

This invention relates to a chuck unit for automatic machine tools, designed to perform both power tasks and high-speed finishing of pieces, with lubricant/coolant fluid flowing through the chuck shaft, which includes:  
     a support ( 1 ) on which a chuck ( 4 ) for a power tool is mounted, the said chuck being driven by a first motor ( 2 )  
     a second chuck ( 5 ) mounted inside the previous one and coaxial with it, which is driven by a second independent motor ( 18 ),  
     means ( 12 ) designed to discharge the pull of the power tool ( 4 ) onto the said support being fitted.  
     The result is a unit which can receive different types of tool and perform different types of task, for which it has so far been most advantageous to use two separate machines.

[0001] This invention relates to a chuck unit for automatic machinetools, designed to perform both power tasks and high-speed finishing ofpieces, with lubricant/coolant fluid flowing through the chuck shaft.For this purpose, the unit in accordance with the invention comprisestwo coaxial chucks fitted one inside the other, driven by separatemotors or by the same motor.

[0002] In particular, the unit in accordance with the invention isdesigned in such a way that when tasks are performed with the powertool, the pull exerted by that tool on the upstream mechanical parts isonly discharged onto the supporting structure of the power chuck, and nostresses are transmitted to the bearings of the second (speed) chuck.

[0003] The result is a unit which can receive different types of tooland perform different types of task, for which it has so far been mostadvantageous to use two separate machines.

[0004] Modern automatic machine tools designed to perform milling andcontouring tasks, etc., comprise a structure to which an operating headwith a number of degrees of freedom is fitted; this head comprises anend effector generally constituted by a chuck or an electric chuck, towhich the tool required for each job is fitted.

[0005] The characteristics of these operating heads vary considerably,especially in chip-forming tasks, depending on whether the tasksperformed are power tasks carried out with a roughing tool which rotatesat a relatively low speed (approx. 2000-3000 rpm) to remove largeamounts of material, and is therefore subjected to considerable stress,or finishing tasks in which the tool rotates at a much higher speed(15-20,000 rpm) to perform a finishing task, and therefore removes smallamounts of material. The stresses to which the tool is subjected and thereactions it discharges onto the upstream devices require the use ofchucks of different characteristics and dimensions, which necessitatesthe construction of different operating heads.

[0006] For this reason, when two different types of task need to beperformed, separate machines are often used, partly because of the timetaken to replace these heads and reset the machine. However, the need isfelt for a machine which can perform both types of task, ie. power andspeed tasks, with no need to replace the operating head or the endeffectors.

[0007] This solution would bring considerable savings, enabling evensmall companies to equip themselves suitably with automatic machines ofthis kind.

[0008] This problem is now solved by the present invention, whichrelates to a chuck unit for automatic machine tools designed to performboth power and finishing tasks. The said unit comprises (i) two chucksmounted coaxially, one inside the other, (ii) means which allow a toolfor roughing work and a tool for finishing work to be fitted to the saidchucks, and (iii) means designed to discharge onto the structure of theassembly the pull exerted on the cone of the tool when the tool isfitted.

[0009] This invention will now be described in detail, by way of examplebut not of limitation, by reference to the enclosed figures in which:

[0010]FIG. 1 shows a cross-section of a chuck unit in accordance withthe invention, with two motors

[0011]FIG. 2 shows a cross-section of the chuck in the rest position

[0012]FIG. 3 shows a cross-section of the chuck unit in thetool-receiving position

[0013]FIG. 4 shows a cross-section of the chuck unit in accordance withthe invention, with the power tool fitted

[0014]FIG. 5 shows a cross-section of the chuck unit in accordance withthe invention, with the finishing tool fitted

[0015]FIGS. 6 and 7 show the chuck unit in accordance with a furtherpreferred embodiment of the invention, with the power and finishingtools fitted

[0016]FIGS. 8 and 9 show a cross-section of the chuck unit in accordancewith the invention, with a single motor;

[0017]FIG. 10 shows a cross-section of a further preferred embodiment ofthe chuck unit in accordance with the invention.

[0018] By reference to FIG. 1, the chuck unit in accordance with theinvention comprises a support structure indicated as 1, to which arefitted an electric motor 2 and the actual chuck unit, indicated as 3 andhoused in a sleeve 33 which is integral with structure 1.

[0019] The chuck assembly comprises a power chuck 4, inside which aspeed chuck 5 is fitted coaxially with the said power chuck.

[0020] Power chuck 4 is fitted to structure 1 via sets of bearings 6,and a pulley or cogwheel 7, to which motion is transmitted by motor 2via a belt 8, is fixed to the said power chuck.

[0021] Chuck 4 presents a conical opening 9 for a power tool, means fordriving the tool being fitted in the said opening.

[0022] The tool is gripped by a gripper 10 shown in FIGS. 2 to 5; thesaid gripper is fitted to the end of a shaft 11 mounted inside speedchuck 5. The axes of shaft 11, chuck 5 and power chuck 4 coincide.

[0023] A set of springs 12 acts against one end of chuck 5 and against ashoulder of shaft 11, pressing shaft 11 inwards, to the position inwhich the said shaft tends to close the gripper in order to clamp thetool applied to the chuck.

[0024] Speed chuck 5, like power chuck 4, has a conical opening at theend shown as 13, in which means designed to drive the tool are fitted,and into which the cone of a finishing tool is inserted.

[0025] In accordance with the invention, the speed tools have a conewhich is inserted into the seating of chuck 5, without coming intocontact with the walls of conical opening 9 of the power tool, while thecone of the power tools is dimensioned so that it can be inserted intothe corresponding seating of chuck 4 without coming into contact withchuck 5.

[0026] Chuck 5 is fitted inside chuck 4 via a set of bearings 15.

[0027] A plate or discoidal element 16 is fitted at the inner end ofpower chuck 4. A sliding grooved bushing 17 is fitted to chuck 5, andmotor 18, which causes finishing chuck 5 to rotate, is mounted on thesaid bushing 17. Bushing 17 widens at the front to define a ring-shapedwall 19 designed to rest against plate 16.

[0028] A set of springs 20, located inside ring-shaped wall 19, act onone side against bushing 17 and on the other against plate 16, tendingto distance bushing 17 from chuck 4.

[0029] Chuck 5 is fitted to structure 1, near the rear end, via bearings21.

[0030] A cylinder 22 in which a piston 23 moves is fitted to the rear ofsleeve 33. Piston 23 is hollow, and a second piston 24 moves inside it.

[0031] Two chambers 31 and 32 are defined on opposite sides of piston24, and two more chambers 35 and 36 are defined on opposite sides ofpiston 23. A bushing 25 is fitted to the rear end of speed chuck 5. Abody 26, which slides inside the said bushing 25, is pushed towards theexterior by a spring 27 which acts between the end wall of bushing 25and body 26.

[0032] Body 26 is hollow; end 34 of shaft 11 penetrates into it on oneside, and a second shaft 28, which is fitted with a gripper, illustratedin FIGS. 2 to 5 and indicated as 30, penetrates into it on the other.

[0033] Bushing 25 comes to rest against bushing 17, which is caused torotate together with bushing 25 by chuck 5.

[0034] Bushing 25 in turn causes body 26 to rotate; the said body 26 canrotate freely in relation to pistons 23 and 24.

[0035] A spring 29 acts on shaft 28, tending to distance it from shaft11.

[0036] The operation of the unit in accordance with the invention willnow be explained, by reference to FIGS. 2 to 5.

[0037]FIG. 2 shows the assembly in the rest position.

[0038] Spring 12 pushes shaft 11 back, with gripper 10 inside chuck 5.

[0039] Springs 20 push bushing 17 back to that a gap of (for example) 1or 2 millimeters remains between ring-shaped wall 19 and plate 16.

[0040] To fit a roughing tool, the assembly is positioned as shown inFIG. 3.

[0041] For this purpose, starting from the position shown in FIG. 2, apressurised fluid is introduced into chamber 32 so that piston 24advances and acts on gripper 30 via shaft 28 to bring the gripper intothe opening position.

[0042] At the same time, a pressurised fluid is introduced into chamber35 so as to advance piston 23, which pushes forward body 26 and shaft11, to open gripper 10.

[0043] The advance of body 26 compresses springs 27, which in turn pushforward bushing 25 and bushing 17, overcoming the force of spring 20,and bring ring-shaped wall 19 into contact with the correspondingseatings in plate 20, thus closing the play between the two parts.

[0044] The power tool is then inserted into conical seating 9 in chuck 4and locked with gripper 10.

[0045] For this purpose, piston 24 is released; the said piston 24 movesbackwards and closes gripper 30, which locks shaft 11 in the positionwhich closes gripper 10.

[0046] Piston 23 is then released, and is pushed backwards to releasebody 26. Body 26 is pushed by springs 27.

[0047] The force exerted by springs 27 acts on shaft 11 on one side, viabody 26 and gripper 30, to lock the tool, while on the other side, viabushing 27 and bushing 17, it keeps ring-shaped wall 19 pressed againstplate 20. It is then possible to start up motor 2, which transmitsmotion via belt 8 to pulley 7, and from there to chuck 4.

[0048] Chuck 4 performs the power task, and the thrust whichcounterbalances the traction force exerted on the tool by shaft 11 tomaintain it in position is discharged onto bushing 17 and from there toplate 20 and chuck 4, without subjecting bearings 15 and 21 of thefinishing chuck to any particular stress.

[0049] When the finishing tool needs to be fitted to chuck 5, the unitis returned to the position shown in FIG. 3, and the cone of the newtool is inserted into seating 13 of chuck 5.

[0050] Piston 23 is then released, moves backwards and releases piston24, thus releasing gripper 30 which disengages from shaft 11.

[0051] The two pistons 23 and 24 move backwards, and springs 27 arereleased. The force of springs 20 then prevails over bushings 17 and 25;the said springs 20 push back bushing 17 and ring-shaped wall 19, thusrestoring the play with plate 20.

[0052] At this point motor 18 of the electric chuck can be switched on.The said motor 18 causes bushing 17 to rotate and finishing chuck 5rotates with it. Finishing chuck 5 can rotate freely on bearings 15 and21.

[0053]FIGS. 6 and 7 show a further preferred embodiment of the chuckunit according to the invention, which has more compact dimensions thanthe one described above and eliminates the need to fit flanges forconveyance of coolant, because the coolant can flow directly throughshaft 11.

[0054] In this configuration, two coaxial cylindrical bodies 41 and 42are fitted to rear plate 40 of sleeve 33, cylinder 41 having a lightlysmaller inner diameter than cylinder 42.

[0055] Internally, cylinders 41 and 42 are shaped to define a pair ofring-shaped chambers 43 and 44 in which two ring-shaped pistons shown as45 and 46 slide.

[0056] Inside cylindrical bodies 41 and 42 there is a bushing 47, fittedto slide on shaft 11.

[0057] The diameter of bushing 47 is larger than the inner diameter ofpistons 45 and 46, and the said bushing 47 acts as a stop for them.

[0058] A flange 48 is also fitted to slide on shaft 11; the outerdiameter of the said flange 48 is substantially equal to the innerdiameter of bushing 47.

[0059] A set of springs 60, which tend to distance bushing 47 fromflange 48, are housed in bushing 47.

[0060] A cylindrical body 61 which supports cylindrical body 49 isfitted to cylindrical body 41. Piston 24 slides in cylindrical body 49,defining two opposite ring-shaped chambers 31 and 32 inside it.

[0061] Shaft 11 projects from bushing 48 and is elongated at the rear sothat it penetrates into a seating in piston 24.

[0062] The unit operates as follows.

[0063] To fit the power tool, start with the configuration shown in FIG.6, with pressurised fluid in chambers 43 and 44. This pressure pushespistons 45 and 46 towards one another; piston 46 strikes wall 65 ofcylindrical body 41, of smaller diameter, while piston 45 strikes theedge of bushing 47, freeing a space which allows shaft 11 to slide.

[0064] Pressurised fluid is then conveyed into chamber 32, thus causingthe movement of piston 24, which pushes forward shaft 11 (to the rightin the figure), opening gripper 10 which is inserted into the cone ofthe power tool shown as P.

[0065] At this point, the pressure is released from chambers 32, 43 and44, causing pressurisation of chamber 31.

[0066] Springs 60 then push flange 48 towards the rear of the chuckunit, and shaft 11 moves with it. This movement of shaft 11 causes thegripper to lock power tool P in its seating.

[0067] Flanges 62 and 63, via springs 64, ensure that pistons 45 and 46return to their end-of-stroke positions against flanges 61 and 42.

[0068] The force exerted by springs 60 overcomes that of springs 20,with the result that on one side springs 60 push bushing 47 to pressagainst bushing 17, thus pushing ring-shaped wall 19 against plate 16,while on the opposite side flange 48 engages the enlarged end of shaft11, shown as no. 50, exerting sufficient force on the shaft tocounteract the thrust discharged by the tool.

[0069] To fit the finishing tool, start with the configuration shown inFIG. 6, with the pressurised fluid in chambers 43 and 44. Bring gripper10 forward again and insert the cone of the finishing tool, whichpenetrates into seating 13, after which the pressurised fluid is onlydischarged into chamber 32, thus pressurising chamber 31.

[0070] Springs 60 remain compressed as a result of the force exerted bypistons 45 and 46.

[0071] In this position, the edge of flange 47 remains a few millimetresaway from flange 17, which can therefore be pushed backwards by springs20, thus interrupting contact between ring-shaped wall 19 and plate 16.

[0072] In this position, shaft 11 is pushed backwards, but this time bysprings 12, which exert the necessary force to clamp the cone of thefinishing tool.

[0073]FIG. 10 shows a further embodiment of the chuck unit in accordancewith the invention, which is more compact and practical.

[0074] In this embodiment the power chuck 4 is actuated by a motor 80,housed inside the sleeve 33.

[0075] The support structure is no more necessary, and this enhances theinterchangeability of the apparatus.

[0076]FIGS. 8 and 9 show a further embodiment of the chuck unit inaccordance with the invention, which is much cheaper than the onedescribed above because electric motor 2, pulley or cogwheel 7 and belt8 are not used; if motor 18 is sufficiently powerful, it can be used forpower tasks as well as finishing tasks.

[0077] In this configuration, power chuck 4 has a male coupling 70 onthe back. Flange 17 has a female coupling 71 on ring-shaped wall 19.

[0078] The unit operates as follows:

[0079] To fit the power tool, always start with the configuration shownin FIG. 6, with the pressurised fluid in chambers 43 and 44.

[0080] Pressurised fluid is then conveyed into chamber 32, thus causingthe movement of piston 24, which pushes forward shaft 11 (to the rightin the figure), opening gripper 10 which is inserted into the cone ofthe power tool shown as P.

[0081] At this point, the pressure is released from chambers 32, 43 and44, causing pressurisation of chamber 31.

[0082] Springs 60 then push flange 48 towards the rear of the chuckunit, and shaft 11 moves with it. This movement of shaft 11 causes thegripper to lock power tool P in its seating.

[0083] Flanges 62 and 63, via springs 64, ensure that pistons 45 and 46return to their end-of-stroke positions against flanges 61 and 42.

[0084] The force exerted by springs 60 overcomes that of springs 20,with the result that on one side springs 60 push bushing 47 to pressagainst bushing. 17, thus causing ring-shaped wall 19 to engage withfemale connector 71 above male connector 70 of chuck 4.

[0085] On the opposite side flange 48 engages the enlarged end of shaft11, shown as no. 50, exerting sufficient force on the shaft tocounteract the thrust discharged by the tool.

[0086] To fit the finishing tool, start with the configuration shown inFIG. 6, with the pressurised fluid in chambers 43 and 44. Bring gripper10 forward again and insert the cone of the finishing tool, whichpenetrates into seating 13, after which the pressurised fluid is onlydischarged into chamber 32, thus pressurising chamber 31.

[0087] Springs 60 remain compressed as a result of the force exerted bypistons 45 and 46.

[0088] In this position, the edge of flange 47 remains a few millimetersaway from flange 17, which can therefore be pushed backwards by springs20, thus interrupting contact between ring-shaped wall 19 and femaleconnector 71, and between chuck 4 and male connector 70.

[0089] In this position, shaft 11 is pushed backwards, but this time bysprings 12, which exert the force necessary to clamp the cone of thefinishing tool. As will be clear from the description given, the chuckunit in accordance with the invention is very useful because it enablestwo different types of job to be performed with a single machine, andallows the operator to change from one to the other in a few secondsmerely by replacing the tool, with no need to use a second machine or toreplace the end effectors, which would involve resetting the zeros,repositioning the workpieces and so on, leading to considerable wastageof time and long machine stoppages.

[0090] An expert in the field could devise numerous modifications andvariations, all of which should be deemed to fall within the scope ofthis invention.

1. Chuck unit for automatic machine tools, characterised in that itcomprises two independent chucks (4, 5), mounted coaxially, designed toreceive different tools, the seatings for the said tools also beingcoaxial and located on the same side of the chuck unit.
 2. Chuck unitfor automatic machine tools as claimed in claim 1 , characterised inthat the said chucks (4, 5) are mounted one inside the other.
 3. Chuckunit for automatic machine tools as claimed in claim 2 , characterisedin that the said chucks (4, 5) are activated by independent motors (2,18).
 4. Chuck unit for automatic machine tools as claimed in claim 2 ,characterised in that it includes a pair of flanges, pushed by elasticmeans (12), which pull the shaft (11) on which the tool cone gripper(10) is fitted into the closed position, and discharge the pull onto thestructure of the assembly.
 5. Chuck unit for automatic machine tools asclaimed in claim 4 , characterised in that it includes: a support (1) onwhich a chuck (4) for a power tool is mounted, the said chuck beingdriven by a first motor (2) a second chuck (5) mounted inside theprevious one and coaxial with it, which is driven by a secondindependent motor (18), means (12) designed to discharge the pull of thepower tool (4) onto the said support being fitted.
 6. Chuck unit forautomatic machine tools as claimed in claim 4 , characterised in thatthe said chucks (4, 5) are driven by the same motor (18).
 7. Chuck unitfor automatic machine tools as claimed in claim 3 , characterised inthat it includes: a support (1); a sleeve (33) fixed to the saidsupport; a power chuck (4) fitted to the said sleeve (33), which saidpower chuck (4) is driven by a motor (2) fitted to the said support; afinishing chuck (5) fitted inside the said sleeve (33) coaxially withand inside the power chuck (4); a shaft being housed inside the saidfinishing chuck (5), at the end of which shaft (11) a tool cone gripper(10) is fitted, the said shaft being subject to the action of springs(12) which tend to push it backwards to lock the said gripper (10); abushing (17) fitted to slide on the said finishing chuck (5) and drivenby the drive motor (18) of the said chuck; means (20) designed to pushthe said bushing (17) in the direction in which the said power (4) chuckretracts; a second bushing (25) fitted to slide on the said finishingchuck (5); a piston (26) fitted inside the said second bushing (25) andsubject to the action of elastic means (27) which engage the end wall ofthe said bushing (25) on one side and the said piston (26) on the other;the action of the said elastic means (27) on one side pushes the saidpiston (26) to strike against stop means fitted in the rear part of thechuck unit, and on the other side pushes the said bushing (25) to engagewith the said bushing (17), thus causing the front edge of the saidbushing (17) to engage power chuck (4) or a wall integral with the saidpower chuck (4); the unit being also equipped with means designed toengage the said s shaft (11) in order to control its travel in relationto the said bushing, and cause gripper (10) fitted to the said shaft(11) to open and lock the cone of the tool which is inserted in thepower chuck or finishing chuck.
 8. Chuck unit for automatic machinetools as claimed in claim 7 , characterised in that it includes a secondpiston (23), coaxial with the said first piston (26), which is designedto engage the said piston (26) and push it to compress the said springs(27), a shaft (28) fitted with a gripper (30) designed to engage therear end of the said first shaft (11) being located inside the saidpiston (23).
 9. Chuck unit for automatic machine tools as claimed inclaim 3 , characterised in that it includes: a bushing (17) fitted toslide on the said finishing chuck (5), which said bushing is able tomove between a position in which it rests with its front edge against aplate integral with the said power chuck (4) and a position in which thesaid bushing retracts from the said plate; a second bushing (47) fittedto slide on shaft (11) behind the said first bushing (17); a flange (48)fitted to slide on shaft (11), which is able to move between a positionin which it approaches the said bushing (47) and a position in which itmoves away from the said bushing (47); a set of springs (60), locatedinside the said bushing (47), which tend to distance the said flange(48) from the said bushing (47); a pair of pistons (46) and (45)situated on opposite sides from the said bushing (47) and the saidflange (48); a piston (24) fitted behind the said bushing (47) anddesigned to engage the said shaft (11) on which tool gripper (10) isfitted; means designed to pump a pressurised fluid into the chambers inwhich the said ring-shaped pistons (45) and (46) are situated, so as topush the said pistons (45) and (46) towards one another, causing one ofthe said pistons (46) to engage a fixed stop (64) and the other (piston45) to engage the said bushing (47), thus positioning flange (48). 10.Chuck unit for automatic machine tools as claimed in claim 3 ,characterised in that a pair of flanges (62) and (63) are fitted betweenthe said ring-shaped pistons (46) and (45), which said flanges aresubject to the action of means (64) that tend to distance them, in orderto separate the said pistons (45) and (46) from the said flanges (47)and (48).
 11. Chuck unit for automatic machine tools as claimed in claim2 , characterised in that it includes: a pair of chucks fitted coaxiailyone inside the other, one designed to receive a power tool and the othera finishing tool a shaft to which a tool cone gripper is fitted abushing fitted to slide on the inner chuck and connected to a drivemotor, which said bushing is fitted with means designed to engage thesaid outer chuck, causing it to rotate thrust means designed to keep thesaid bushing distanced from the said outer chuck a pair of flanges,pushed by springs, which pull the shaft on which the tool cone gripperis fitted so as to close the said gripper, discharging the pull onto thestructure of the assembly means designed to act on the said bushing,counteracting the force exerted by the said thrust means so as to pushthe said bushing to engage with the said outer chuck.
 12. Tools for achuck unit in accordance with claim 1 , characterised in that the partof the cone between the connector for the gripper and the body of thetool is of such dimensions as to engage the corresponding seatingwithout interfering with the seating of the second chuck.
 13. Chuck unitfor automatic machine tools as claimed in claim 5 , characterised inthat said speed chuck (5) is mounted inside said power chuck (4). 14.Chuck unit for automatic machine tools as claimed in claim 3 ,characterised in that said power chuck (4) is moved by a motor (80)house inside the said sleeve (33).